Controllable shape hull structure



June 1965 v. w. FRIES 3,190,587

CONTROLLABLE SHAPE HULL STRUCTURE Filed March a, 1963 s Sheets-Shee t 1 June 22, 1965 v. w. FRIES 3,190,537

CONTROLLABLE SHAPE HULL STRUCTURE Filed March 8, 1963 5 Sheets-Sheet 2 any memo? June 22, 1965 v. w. FRIES 3,190,587

CONTROLLABLE SHAPE HULL STRUCTURE Filed March 8, 1963 I 3 Sheets-Sheet 5 ,4 r roFMeYJ United States Patent 3,190,587 CGN'IRUIJLABLE SHAPE HULL STRUCTURE Vollmer W. Fries, 1250 Edgewater Drive, Cleveland, Ohio Filed Mar. 3, 1963, Ser. No. 263,897 9 Elaims. (Cl. 244-406) This invention relates generally to hull structures for boats, ships, and aircraft, and more particularly to a novel and improved hull structure incorporating inflat able means operable to change the hull shape for maximum efliciency for various types of operation.

This invention provides a hull incorporating means to alter the shape of a boat or aircraft hull at the Will of an operator to best suit the existing operating conditions. Means are provided to improve the operating characteristics of the hull, as to performance, control, safety comfort, and buoyancy, by providing the hull with an outer flexible skin that can be, when deflated, positioned snugly adjacent to the rigid structure and when inflated expands to alter the underwater lines a predetermined amount, thereby giving the hull wide adaptability to changing wind, sea, and operating conditions.

A boat hull incorporating this invention includes means which can be inflated to change the hull from a displacement hull to a planing hull or from a planing hull to a displacement hull thereby providing the operator with a selection of hull shapes within a single hull so that the optimum hull shape can be provided for whatever type of operating conditions exist at any given time.

invention is also useful to change the shape of the hull or floats of aircraft so that the aircraft is provided with a minimum drag when flying through the air while still providing the necessary hull shape for water operation thereof, during take-offs and landings. Still further this invention contemplates providing means on ships to increase the displacement of the ship to reduce the draft for operation in shallow water.

It is an important object of this invention to provide a novel and improved hull incorporating means to modify the hull shape at the will of the operator to provide an optimum hull shape for the operating conditions existing at any given time.

It is another important object of this invention to provide a novel and improved hull having means inflatable and deflatable at the will of the operator to change the hull shape providing maximum efliciency for a variety of operating conditions.

It is another important object of this invention to provide a novel and improved hull combination including a rigid hull shaped to efliciently operate at one speed condition and including means inflatable to change the shape of the hull so that it will operate efficiently at speed conditions substantially diiferent than such one speed condition.

It is still another object of this invention to provide a novel and improved hull assembly including a rigid displacement hull in combination with inflatable means for changing the underbody shape of the hull to a planing type hull.

It is still another object of this invention to provide a novel and improved hull combination having a rigid planing type hull structure in combination with means inflatable at the will of the operator to change the underbody shape of the hull to a displacement hull shape.

It is still another object of this invention to provide a novel and improved hull for aircraft which includes means inflatable and deflatable at the will of the pilot, to provide a minimum drag shape while the aircraft is flying and an efficient hull shape for the water operation of landing, taxiing, and take-off.

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It is still another object of this invention to provide. a novel and improved hull having means inflatable to increase the displacement of the hull and reduce the draft for operation in shallow harbors, streams and the like.

It is still another object of this invention to provide a novel and improved inflatable structure for hulls of boats, aircrafts, and ships, including inflatable means which snugly lay along the hull structure when deflated and which can be inflated to a predetermined shape, substantially changing the dynamic characteristics of the hull moving through a fluid medium.

It is still another object of this invention to provide a novel and improved hull structure having flexible, substantially non-elastic panels mounted thereon, and cooperating therewith to form inflatable means having a predetermined shape upon inflation.

Further objects and advantages will appear from the following description and drawings wherein:

FIGURE 1 is a side elevation of a displacement hull for a small boat incorporating this invention illustrating the hull with the inflatable means deflated;

FIGURE 2 is a view similar to FIGURE .1 of the hull appearing therein illustrating the hull with the inflatable means inflated to present a planing underbody thereon;

FIGURE 3 is an end view of the hull illustrated in FIGURE 1;

FIGURE 4 is an end view of the hull illustrated in FIGURE 2;

FIGURE 5 is an enlarged fragmentary cross-section View taken along 5'5 of FIGURE 1, illustrating the inflatable means in the deflated condition;

FIGURE 6 is an enlarged fragmentary cross-section taken along 6-6 of FIGURE 2, illustrating the inflatable means in the inflated condition;

. FIGURE 7a is an enlarged fragmentary cross-section of the folding section of FIGURE 5, illustrating the structural detail of one form of the inflating means in the de flated condition;

FIGURE 7b is an enlarged fragmentary view of the hinge section of FIGURE 6 showing the structure in the inflated position;

FIGURE 8 is an end view of a second embodiment, a boat hull, wherein the hull is a planing type hull when the inflatable means is deflated;

FIGURE 9 is a view similar to FIGURE 8, illustrating the hull when the means are inflated to change the hull shape to a displacement type hull;

FIGURE 10 is an enlarged fragmentary cross-section illustrating the structure of the hull of FIGURE 9 with the hull inflated to the displacement shape;

FIGURE 11 is an enlarged fragmentary view showing the structural detail of the inflation means in the deflated condition occurring when the hull is in the condition of FIGURE 8;

FIGURE 12 is a schematic illustration of the pressure system for inflating and deflating the inflation means;

FIGURE 13 is a side elevation of a flying boat provided with means'to change the hull shape when the aircraft is airborne for the reduction of drag illustrating the hull in the deflated condition for landings and take-offs;

FIGURE 14 is a view similar to FIGURE 13, illustrating the inflation means inflated to reduce the drag of the aircraft while flying;

FIGURE 15 is a cross-section taken along 15-15 of FIGURE 14;

FIGURE 16 is a cross-section taken along 16-16 of FIGURE 14;

FIGURE 17 is a side elevation of a float aircraft, illustrating another form of this invention in which the float can be deflated when aircraft is airborne to reduce drag;

FIGURE 18 is an enlarged section taken along 1818 of FIGURE 17, illustrating the structural detail of a pr ferred form of float in the inflated condition for operation on water;

FIGURE 19 is a view similar to FIGURE 18, ing the float in the deflated condition in hich of the float .is substantially decreased;

FIGURE 20 is a schematic section of a ship hull incorporating inflatable means operable to increase the displacement of the hull and thereby reduce its draft for operation in shallow waters and harbors; and

FIGURE 21 is an enlarged fragmentary section of the inflation means of the hull of FIGURE 20, illustrating the inflation means in the deflated condition.

There are three general types of boat hulls; displacement hulls, planing bulls, and combination semi-displacement semi-planing hulls. All boat hulls, when stationary in water, displace a volume of the water having a weight equivalent to the weight of a boat and its payload. Differences in hull design result in different performance and different power requirements when they are driven through or over the Water. A displacement hull is designed to proceed through the water with its displacement of water remaining approximately the same from a stationary condition up to its maximum speed. Its hull form, when well designed, proceeds through the water with a minimum disturbance of the water parting at the bow and rejoining astern. At low speeds, in relation to the lengthbeam ratio, it handles well and is seaworthy. When well designed, it is comfortable in a seaway and requires a minimum horsepower for a given speed Within the slow speed range. As the speed is increased beyond its efficient cruising speed, which is determined largely by the length, assuming the length-beam ratio and the basic hull lines stay about the same, the rate of disturbance of the water that parts and rejoins as the boat moves increases and the power required to secure an additional speed goes up rapidly. Therefore, displacement type hulls have practical maximum speeds which cannot be exceeded without the use of prohibitively excessive power.

A planing hull is designed so that its underbody will present two inclined planes to the water, one on each side of the keel. These planes supply dynamic lift which is related to the speed of the boat. When this hull type reaches a speed where it is said to be planing, the hull is proceeding more on the water than in the water and the dynamic lift is much greater than the displacement or buoyancy lift. In this planing condition the speed to power ratio is much greater than with a displacement hull. In fact, with a planing hull, speeds can be achieved which are two and one half to three times the practical speeds achievable with a displacement hull of the same weight and horsepower. The relative disadvantages of the planing hull are that it does not handle well at low speeds, it is relatively inefiicient on a power speed ratio basis at low speeds, and in a seaway of sufficient wave height to prevent safe use of planing speed it is relatively less seaworthy and certainly more uncomfortable due to pounding and hobbing.

The combination hull is basically a displacement hull with certain modifications in its design to acquire some of the advantages of a planing hull. Generally this is done by adding beam, at relatively wider stern, and a flatter underbody from the midship to the stern. By this means some dynamic lift at the upper end of its speed range is achieved while still retaining a substantial portion of the round bottom characteristics. Such hulls are, at most, compromises since they do not provide the best features of either planing or displacement and provide some of the disadvantages of each.

FIGURES 1 through 11 illustrate two embodiments of this invention. In FIGURES 1 through 711 a hull of the displacement type is illustrated having inflatable means to change the underbody of the hull to a planing type. The second embodiment of FIGURES 8 through 11 illustrates a hull having a rigid planing shape which can be illustratthe drag [5. changed by inflation means to a displacement shape at the will of the operator.

In the embodiment of FIGURES 1 through 7b a rigid hull 1G is provided with inflation means 11 which when deflated lay snugly against the hull 10, as illustrated in FIGURES 1, 3, 5 and 7a. In this condition a roundbottom or underbody 12 is provided so that the hull 10 will move smoothly and efiiciently through the water at low operating speeds. When pressure is supplied to the inflation means 11 they are inflated to present two generally planar surfaces 113 with one on either side of the keel 14. These planar surfaces 13 are proportioned and arranged so that the application of sufficient power will cause the hull to ride up out of the water in the condition known as planing. In such a condition the hull is supported primarily by the lift created by the planar surfaces passing over the water and the displacement of the hull is drastically reduced.

With this hull the operator can select the underbody hull shape he desires to most efliciently operate the boat under either slow-speed displacement operation or highspeed planing operation. In the event that the sea is sufficiently high to prevent practical planing operation the inflation means 11 are deflated to present a displacement underbody to the water. This substantially reduces the bobbing and increases the seaworthiness of the hull.

The structure of one form of the inflation means is best illustrated in FIGURES 5 through 7b. Since the hull and the inflation means are symmetrical about the keel 14 only one side of the hull is illustrated. Inflation means 11 includes a flexible substantially non-elastic panel 16 joined at 17 adjacent to the keel 14, to a mounting sheet 13. Preferably the panel 16 is formed of rubber-like material having layers of fabric 19 embedded therein to prevent elasticity and increase strength while still permitting flexibility. The sheet 18 is preferably formed of thin rubberlike material secured along the lower side of the hull 10 by a suitable adhesive or other fastening means, depending upon the material from which the rigid hull is made.

A chine panel 21 is bonded to the mounting sheet 17 at 22 and to a hinge extrusion 23 along its lower edge. The hinge extrusion 23 is also preferably formed of a rubber-like material. It is extruded with an unstressed shape as illustrated in FIGURE 7a, and deflectable when the inflation means is pressurized to the position of FIG- URE 7b. Therefore, the hinge extrusion 23 functions as a hinge and in addition as a spring resiliently urging the connected elements to the folded deflated position of FIGURE 7a. A fold panel 24 is connected between the hinge extrusion 23 and a second hinge extrusion 26. The second hinge extrusion 26 is, in turn, connected to the lower panel 16. The hinge extrusion 26 is also formed of rubber-like material extruded to an unstressed shape as shown in FIGURE 7a, so it also serves the dual function of a hinge and spring urging the fold panel toward the folded position of FIGURE 7a.

As illustrated in FIGURE 6 the mounting sheet 17 in cooperation with the panels 21, 24 and 16, along with the hinges 23 and 26, form a fluid tight chamber 27 which is pressurized to inflat the inflation means and cause the various panels to assume the position of FIGURES 4 and 6. When the pressure in this chamber is released the panels fold against the rigid hull 10 as illustrated in FIG- URES 3 and 5. The two hinges 23 and 26 act as springs, urging the fold panel toward the folded position of FIG- URE 5 insuring that proper folding movements will occur as the pressure is released from the chamber 27. The chine panel 21 and the fold 24 are preferably formed of a material similar to the panel 16 so that they are substantially non-elastic but deflectable.

The panels 16 and 21 are contoured so that they have additional thickness adjacent to the hinge area to insure that a smooth contour will be provided when the panels move to the folded position of FIGURE 5. The thickening of the panel 16 is preferably internal and the thickening of the panel 21 is external as illustrated. This thickening of the panel 21 provides a shoulder 28 serving as a splash rail when the chamber 27 is pressurized to move the panels to the planing shape of FIGURE 4.

To assure that the panels 16, 21 and 2d are properly positioned in the desired planing shape a plurality of tension straps 29 are connected between the mounting sheet 18 and the respective panels to anchor the panels against the extending pressure within the chamber 2'7 when they reach the proper inflated position. Preferably the tension straps 29 are formed of a thin, high strength material, such as glass cloth, which folds easily when the chamber 27 is deflated but provide extremely high strength to support tension loads. The tension straps 29 are located in a manner to insure that the lower panel 16 will provide a flat planing surface and the side panels 21 and 24 will be maintained in their aligned condition. The material forming the panels 16, 2]. and 24-, must be flexible so that they can assume the two positions required, but should be sufficiently stiff so that an excessive number of tension straps need not be provided.

Preferably air pressure is used to inflate the chamber 27 so a pressure line 31 connects the chamber 27 to a source of fluid under pressure. Referring to FIGURE 12, one system for inflating and deflating the inflation means is illustrated schematically. A compressor 32 is connected to the motor of the boat to supply air pressure to a reservoir tank 33. An automatic regulator (not shown) is connected to the compressor 32 to unload the compressor whenever the pressure in the tank 33 reaches a predetermined value. Also, a suitable back-check valve is provided to prevent backflow from the tank. The outlet from the tank 33 is connected to a pressure regulator 34 which reduces the output pressure to the pressure required to inflate the inflation means. Downstream from the pressure regulator is a valve 36 which selectively connects the chambers 27 to the outlet of the pressure regulator or to an atmospheric exhaust 3'7. When the valve 36 is in the position illustrated, air pressure is supplied to the chambers 27 to move the panels to the inflated position. When the valve 36 is turned to its other position, the chambers 27 are isolated from the pressure regulator 34 and connected to the exhaust 37 to deflate the chambers.

Two pressure lines Ell are illustrated connected through a T to the valve 36, and these represent the two chambers 27 one on either side of the keel 14. In some structures a single inflation means may be provided extending the full width of the hull or more than two separate inflation means may be provided. In such installation the manifolding is modified to the particular structure. It should also be understood that the illustrated pressure supply system of FIGURE 12 may be modified to meet the particular design requirements encountered. As an example, in small boats a pressure tank may be pressurized at dockside from a shore compressor rather than by a compressor located on the boat. in such case, the tank has suflicient volumetric capacity to pressurize the chambers 27 a sutiicient number of times to meet the expected cruise operation of the boat. Such a system is provided on boats where cost, weight and space are important considerations. In some boat installations a hand pump is used to supply the required pressure. it should be understood that the pressure supplied to the chamber 27 need not be particularly high and is normally less than pounds per square inch. In most instances the inflating fluid is air under pressure but in some cases liquid under pressure may be used for inflation. As an example, water may be used for inflation if optimum weight distribution requires additional weight in certain areas.

Since the planing surfaces are pressure supported, shock absorption is provided. Therefore, the hull is protected against damage by pounding during planing operations and a softer ride is achieved. Also, the rubberlike material forming the bottom surface or underbody of the boat reduces the likelihood of damage if an obd struction is encountered, since such materials are extreme- 1y tough and resistant to abrasion. It should be understood that the particular structure illustrated may be modified to meet the shape and size requirements of a particular hull shape and size, and that the illustrated structure is only representative of one preferred form.

All drawings are of the simplified diagrammatic type, in recognition of the fact that the ultimate in advantages to be gained through the use of this invention will arise principally when the naval architect, boat designer or aeronautical engineer designs the lines of the rigid hull of the boat or aircraft for maximum desired performance characteristics for one set of conditions in anticipation of the use of this invention to secure another set of desired hull or airframe lines when the inflatable skin is fully inflated, or intermediate sets of hull or airframe lines at points of partial inflation.

Reference should now be made to FIGURES 8 through 11, which illustrate another embodiment of this invention wherein a planing hull is provided when the inflation means are deflated and a displacement type hull is provided when the inflation means is inflated. The rigid hull 4-1 is provided with substantially flat-bottom panels 42 on either side of the keel 43. When the inflation means 49 are deflated they fit against the bottom panels 42 to provide flat planing surfaces 44.

In this embodiment the mounting sheets 46 are bonded to the hull 51 by adhesive or other suitable mounting means and extend from adjacent to the keel 4-3, along the bottom 42, and up along the chines 47 are best illustrated in FIGURE 10. Similar and opposite main panels 48 are connected by a hinge strip 49 to the mounting sheet 46 along the joint between the chines 47 and bottom panels 42. Here again the hinge strip 4% is preferably formed as an extrusion having an unstressed shape similar to the shape the hinge assumes when the panel 58 fits along the mounting sheet 45. Adjacent to the keel 43 a fold panel 51 is bonded to a hinge strip 52 providing a double hinge joint between the panels 43 and 51, and also between the fold panel 51 and a U-shaped, rigid keel cover 53. A similar hinge strip 52 is provided on either side of the keel, as illustrated in FIGURE 11, and is preferably formed with an unstressed shape as illustrated in that figure so that the various elements are resiliently urged toward the folded position of FIGURE 11 wherein the fold panels 51 fit snugly against the sides of the keel 4-3, and the main panels 44 fit along the bottom panels 42 of the hull ll.

in this embodiment a single chamber 54 is defined by the mounting sheets 46 in cooperation with the two main panels t3, the two fold panels 51, the keel cover 53, and the hinge strips 49 and 52, extending the complete distance across the bottom or" the hull 41. A pressure line 56 connects to the chamber 54 and the pressure control system which may be of the type illustrated in FIG- URE 12. When air pressure is supplied to the chamber 54 the main panels 33 extend down, away from the bottom panel of the hull 41 to the position of FIGURE 10. When this occurs the fold panels 51 move to a position substantially aligned with the adjacent edge of the main panels and the keel cover 53 moves down along the keel 43 to the illustrated position, Preferably the keel cover 53 still embraces the bottom edge of the keel 43 to provide stability when the chamber 54 is pressurized. Here again tension strips 57 are connected between the mounting sheet 45 and the main panels 48 to insure that the main panel will be precisely positioned when the chamber 54- is pressurized. It should be understood that the pressure strips are either provided with openings or do not extend the full length of the panels 43 so that they do not isolate various portions of the chamber 54.

In this embodiment the planing shape is provided when the chamber 54 is depressurized and the panels fit snugly against the rigid hull 41, and pressurization of the chamher 54- moves the panels to a position wherein a displacement type underbody is provided. This particular embodiment has the advantage of providing additional displacement when the boat is used as a displacement hull and will result in more free-board under thi condition. This is particularly desirable since the displacement hull underbody is often used in rough water, so a maximum displacement is provided for rough water operation and a minimum displacement is provided for high-speed planing operation when a low wind resistance profile is desirable. Here again the tough protective layer of the rubber-like panels also protects the rigid hull t l against damage due to impacts with obstacles in the water, and the like.

In FIGURES 13 through 16, another embodiment of this invention is illustrated wherein inflation means are provided on the hull of a flying boat to improve the operating characteristics thereof. The lower hull form of a flying boat must be shaped for etlicient water operation during take-offs and landings. Generally the shape is arranged so that the hull planes on the water during the take-off run as the flying speed is attained. Also, the hull planes immediately after landing so that the drag does not produce damaging or dangerous deceleration. This hull shape, however, is not the most efiicient for operation of the aircraft in the air at crusing flying speeds. Ideally the aircraft should have a shape which produces the minimum of drag as it moves through the air. Generally speaking this optimum shape eliminates re-entrant sections which would produce unnecessary turbulance permitting the air to flow smoothly past the aircraft. In this embodiment an inflatable boot 61 is adhesively or otherwise connected to the aircraft hull 2 along a line 63 adjacent to the underbody of the hull 62. Preferably the boot 61 is formed so that it conforms to to the shape of the underbody 64 of the hull 62 when in its unstressed condition, and is deflectable when inflated to form a smooth streamlined shape as illustrated in FIGURE 14.

The pilot of such an aircraft inflates the boot 61 by supplying air pressure to a chamber 65 formed by the boot 61 and the underbody 64 of the aircraft, causing the boot 61 to move away from the underbody 64 and form a smooth streamlined hull shape adjacent to the underbody 64. Before landing the pilot exhausts the chamber 66 and the boot assumes its natural shape against the underbody of the aircraft, as illustrated in FIGURE 13, and the aircraft is in the landing configuration for water operation. Normally a step 67 is formed in the underbody 64 which would produce air turbulence and unnecessary drag if it remained when the aircraft was airborne. Therefore, the boot a1 is provided with sufficient elasticity in this area to permit it to stretch to the inflated position of FIGURES 14 and 16, to eliminate the step during flight operation. The boot in this embodiment generally does not require tension straps since the infiated boot tends to automatically assume a curved, streamlined shape. However, if the aerodynamics of the hull require specific local positioning not achieved by the simple inflation of the boot, straps of a type similar to the straps illustrated in the other embodiments may be utilized. Here again considerable hull protection is provided by the boot 61.

Reference should now be made to FIGURES 17 through 19, which illustrate another embodiment of this invention as applied to the floats of a float type aircraft. The use of floats on aircraft in the past have produced substantial reductions in the operating efficiency since the floats add considerable weight and drag. In the illustrated embodiment the floats '71 are constructed with a rigid core 72 extending the length of the float. The core is generally rectangular modified so that a low drag profile will be presented when the aircraft is flying. The floats are provided with substantially non-elastic relatively flexible side panels 74a and 74b and upper and lower hinge or fold panels 16 7'7 respectively. A top panel '73 is bonded to the upper wall 79 of the core '72 and a bottom panel 81 is bonded to the lower wall 73 of the core. Preferably, the lower wall 73 and in turn the bottom panel 81 are formed with a V shape for efiicient water operation. Hinges 32, preferably formed of extruded rubber-like strips, connect the fold panels 76 to the top panel 78, hinges 83 connect the fold panels to the side panels 74b, hinges 35 connect the side panels 74:: to the lower fold panels 77, and hinges 84- connect the hottoa or lower fold panels 77 to the bottom panel 81. The panels and hinges all cooperate to form a pressure-tight chamber $7 which can be inflated by the pilot of the aircraft through the pressure r line 9 t extending down one of the struts 88 connecting the chambers 67 to a controlled source of pressure in the aircraft.

In order to permit the panels to fold inward, the sides are formed of two pieces 74a and 74!) joined by the hinge 740. In this embodiment tension straps 93 are connected between the various panels and the core 72 to insure that the panels will be maintained in their proper inflated position, illustrated in FIGURE 18, when pressure is supplied to the chambers 87. Here again each of the hinges connecting the various panels is molded with an unstressed shape approaching the shape each hinge assumes when the float is collapsed, as illustrated in FIGURE 19, so that the panels are resiliently urged toward the collapsed condition.

A comparison of FIGURES 18 and 19 will clearly illustrate that the drag of the float is greatly reduced when the panels are folded against the core 72 during the light, thus substantially reducing the drag of the floats during this stage of operation. Preferably, the floats should be sized so that they will support the aircraft even when the chambers 87 are deflated to provide a fail-safe system. However, the added buoyancy, when the chambers 37 are inflated, provides better support of the aircraft during landings, takeofls and taxiing on rough water.

The inflatable structure may also be arranged so that the normal planing step is provided when the chambers 87 are pressurized but a smooth streamlined low drag contour is provided when the chambers 87 are deflated.

In operation the pilot exhausts the chambers 87 when the aircraft is airborne after take-off, allowing the float to assume the folded or stowed position of FIGURE 19. Then, prior to landing, the pilot pressurizes the chambers 87, inflating the float to its landing and water operating conditlon. Preferably the panels of this embodiment are again formed of rubber-like fabric reinforced material and the hinges are formed of extrusions of rubber-like material.

In FIGURES 20 and 21, this invention is illustrated in an embodiment adapted to increase the displacement of a ship to reduce its draft for operation in shallow waters of harbors, rivers, and the like. When designing the hull of a ship it is desirable to determine the hull shape for maximum efficiency during the cruising operation in deep water. However, since such ships must enter harbors, and the like, to load and unload the cargo, consideration must be given to the draft of the ship. By utilizing this invention the hull shape of the ship can be designed for optimum shape for cruising in deep water where the draft of the ship is not important, while still providing a hull which can be operated in sheltered areas of harbors, and the like, with reduced draft. In this embodiment of this invention the ship is formed with a hull 161 shaped for maximum efficiency in deep water operation. A boot m2 is secured along each side of the hull adjacent to the bottom ill?) thereof. Preferably the boots 1&2 are connected along one edge at 104 by adhesive or other suitable fastening means and at the opposite edges 161: to the sides of the hull in normal operation the boot 1G2 tits snugly against the hull 101, as illustrated in FIGURE 21, with a fold at 197 and 168.

The boot Hi2 may be formed of separate panels joined by hinges in the manner described above, or may be formed of a single sheet of rubber-like fabric reinforced material, or the like, having natural hinge sections molded thereinto at ill"! and 103. When the boot 192 is in the folded condition of FIGURE 21 it provides substantially no resistance to movement of the hull 101 through the water and, in fact, tends to reduce friction since the boot is formed with a smooth surface. When the ship is to enter shallow areas where reduced draft is required air pressure is supplied to the interior of the boots N2 causing them to inflate to the condition of FIGURE 20, thus causing a substantial increase in the displacement of the ship and thus reducing its draft.

Tension straps 1&9 are connected between the hull and the inner surface of the boot to insure that the boot will assume the illustrated position when inflated. It should be noted that the straps 169 are arranged to hold the boot down against upward movement which would naturally tend to occur due to the higher water pressure along the lower side of the boot. This insures that the boot 102 will be retained in the desired position for maximum displacement. Also, the straps are arranged to prevent the boot from projecting below the plane of the bottom 103 of the hull 1G1. Because the boots 162 extend laterally from the sides of the hull ltllt adjacent to its bottom 183, the stability of the hull is maintained even under shallow draft operation. 1

The various embodiments of this invention described above are merely illustrative of several applications of this invention to specific structural embodiments and it should be understood that the particular structural arrangements required for a particular embodiment must be adapted to the conditions required by such embodiment. Therefore, although preferred embodiments of this invention are illustrated, various modifications and rearrangements of parts may be resorted to without departing from the scope of the invention as defined in the following claims.

What is claimed is:

l. A hull comprising a rigid frame, a plurality of semi-rigid panels mounted on said frame, rubber-like hinge strips interconnecting said panels for movement between a folded position adjacent said frame and an extended position spaced therefrom, said panels forming at least a part of the underbody of said hull, said hinge strips being substantially unstressed when said panels are in said folded position and under substantial stress when said panels are in said extended position, said panels and hinge strips cooperating to define at least a part of a fluid tight pressure chamber, flexible nonelastic stop means connected between said rigid frame and panels preventing movement of said panels away from said frame beyond said extended position, and pressure means connected to said chamber operable to supply fluid under pressure thereto to cause said panels to move to said extended position.

2. A hull comprising a rigid frame, inflatable means including a mounting sheet secured to said frame and flexible nonelastic sheets secured to said mounting sheet and cooperating therewith to define a fluid tight inflatable chamber, said flexible sheets defining at least a portion of the underbody of said hull, said flexible sheets being positioned adjacent said mounting sheet when said chamher is exhausted and being spaced therefrom when said chamber is pressurized, a controlled pressure source connected to said chamber operable to selectively pressurize and exhaust said chamber, and flexible nonelastic tension means connected between said flexible sheets and said mounting sheet limiting the extent of spacing therebetween when said chamber is pressurized.

3. A hull comprising a frame, an inflatable cover on said frame collapsible to a first position substantially against said frame and inflatable by fluid under pressure to a second position where at least a portion of said cover is spaced from said frame, fluid pressure control means connected to said cover operable to move said cover between said first and second positions, said cover when in one of said positions forming a planing hull and in the other of said positions forming a displacement hull, said cover being formed of fluid tight panels of reinforced substantially non-elastic flexible material joined by hinged portions permitting movement thereof between said positions, and flexible nonelastic tension means holding said panels in said second position against the action of said fluid under pressure.

4. A boat hull construction for operating efficiently over a wide range of operating speeds, comprising a rigid frame shaped as a displacement hull curved along its bottom for efficient operation when substantially the entire weight of the hull is supported by buoyancy, a flexible cover along said bottom of said frame formed with an inflation chamber, said cover when said chamber is deflated being positioned along said bottom of said frame conforming substantially to the shape thereof, said cover when said chamber is pressurized moving to a planing position spaced from portions of said frame and forming flat planing surfaces.

5. A boat hull construction for operating efficiently at low speeds and also operating efficiently at planing speeds comprising a rigid frame shaped as a displacement hull curved along its bottom for eflicient operation when substantially the entire weight of the hull is supported by buoyancy, a flexible cover along said bottom of said frame formed with an inflation chamber, said cover when said chamber is deflated being positioned along said bottom of said frame conforming substantially to the shape thereof, said cover when said chamber is pressurized moving to a planing position spaced from portions of said frame and forming substantially flat planing surfaces, said cover including an inner sheet secured to said frame and outer flexible panels cooperating therewith to form said chamber, said panels being formed of flexible substantially non-elastic material, and rubber-like hinge means connecting said panels resiliently urging said panels toward said frame.

6. A boat hull construction for operating efficiently at low speeds and also operating efliciently at planing speeds comprising a rigid frame shaped as a displacement hull curved along its bottom for efficient operation when substantially the entire weight of the hull is supported by buoyancy, a flexible cover along said bottom of said frame formed with an inflation chamber, said cover when said chamber is deflated being positioned along said bottom of said frame conforming substantially to the shape thereof, said cover when said chamber is pressurized moving to a planing position spaced from portions of said frame and forming substantially flat planing surfaces, said cover including an inner sheet secured to said frame and outer flexible panels cooperating therewith to form said chamber, said panels being formed of flexible substantially non-elastic material, rubber-like hinge means connecting said panels resiliently urging said panels toward said frame, and tension means limiting movement of said panels away from said frame under the influence of pressure in said chamber insuring proper position thereof when said chamber is pressurized.

7. A boat hull construction for operating eflrciently at low speeds and also operating efficiently at planing speeds comprising a rigid frame shaped as a planing hull having substantially flat bottom surfaces for efficient operation at planing speeds, a flexible cover along said bottom of said frame formed with an inflation chamber, said cover when said chamber is deflated being positioned along said bottom of said frame conforming substantially to the shape thereof, said cover when said chamber is pressurized moving to a curved displacement position spaced from portions of said frame, said cover including an inner sheet secured to said frame and outer flexible panels cooperating therewith to form said chamber, said panels being formed of flexible substantially non-elastic material, hinge means connecting said panels normally urging said panels toward said frame, and tension means limiting movement of said panels away from said frame under the influence of pressure in said chamber insuring proper position thereof when said chamber is pressurized.

8. A flying boat hull structure comprising a rigid frame having an underside having a forward planing portion and a step at the rearward end thereof for ei-ficient operation on Water, a flexible boot mounted on said underside of said hull normally positioned therealong and conforming to the surface of said planing portion and step, said boot defining at least a portion of a pressure chamber, a source of pressure connected to supply fluid under pressure to said chamber, pressure in said chamber causing said boot to move away from said underside of said hull and assume a smoothly curved convex shape streamlined for efficient movements through air.

9. A flying boat hull structure comprising a rigid frame having an underside having a forward planing portion and a step at the rearward end thereof for efiicient operation on water, a rubber-like boot mounted on said underside of 12 said hull having an unstressed shape similar to said underside whereby said boot normally extends adjacent said underside conforming to the surface of said planing portion and step, said boot defining at least a portion of a pressure chamber, a source of pressure connected to supply fluid under pressure to said chamber, pressure in said chamber causing said boot to move away from said underside of said hull and assume a smoothly curved convex shape streamlined for efiicient movements through air.

References Cited by the Examiner UNITED STATES PATENTS 1,802,996 4/31 Wurth 244l07 2,429,992 11/47 Crispell 244105 X 3,004,737 10/61 Boyle et al 114-l05 X 3,029,046 4/62 Blaes et a1. 244105 3,076,204 2/63 Nowak 11466.5 X

MILTON BUCHLER, Primary Examiner.

ANDREW H. FARRELL, Examiner. 

8. A FLYING BOAT HULL STRUCTURE COMPRISING A RIGID FRAME HAVING AN UNDERSIDE HAVING A FORWARD PLANING PORTION AND A STEP AT THE REARWARD END THEREOF FOR EFFICIENT OPERATION ON WATER, A FLEXIBLE BOOT MOUNTED ON SAID UNDERSIDE OF SAID HULL NORMALLY POSITIONED THEREALONG AND CONFORMING TO THE SURFACE OF SAID PLANING PORTION AND STEP, SAID BOOT DEFINING AT LEAST A PORTION OF A PRESSURE CHAMBER, A SOURCE OF PRESSURE CONNECTED TO SUPPLY FLUID UNDER PRESSURE TO SAID CHAMBER, PRESSURE IN SAID CHAMBER CAUSING SAID BOOT TO MOVE AWAY FROM SAID UNDERSIDE OF SAID HULL AND ASSUME A SMOOTHLY CURVED CONVEX SHAPE STREAMLINED FOR EFFICIENT MOVEMENTS THROUGH AIR. 